Italian prosecutors asked the country's highest criminal court on Tuesday to reinstate the murder convictions of American Amanda Knox and her former boyfriend in the brutal slaying of a British student.

Perugia prosecutors filed the 112-page appeal, more than four months after an appeals court threw out the convictions against Knox, 24, and Raffaele Sollecito, 27.

Prosecutor Giovanni Galati said he is "very convinced" that Sollecito and Knox are responsible for the Nov. 1, 2007, stabbing death of Meredith Kercher, a 21-year-old British student who shared an apartment with Knox in the university town of Perugia.

Galati told reporters in Pergugia that the appeals sentence must be thrown out, saying it was full of "ommissions and many errors," the news agency ANSA reported.

The prosecutors appeal, which was expected, marks the third and final stage in the criminal case against Knox and Sollecito.

The two were found guilty in a lower court of slaying Kercher in what prosecutors described as a sex-fueled attack, and sentenced to 26 years and 25 years respectively. An appeals court then said the evidence did not hold up, freeing Knox to return home to the United States after serving four years in prison. Sollecito lives in Italy.

Luca Maori, Sollecito's lawyer, said the high court is expected to issue its decision toward the end of the year.

High court to issue decision

The prosecutors move was expected, and Maori said he would file his counter-arguments after going over the prosecutors' appeal.

"We will write our brief to say it's a mistake," Maori said.

The high court cannot hear new evidence, and will make its decision based on what has been submitted in earlier trials.

The fatal blow to the prosecution's case was a court-ordered DNA review in the appellate trial that discredited crucial genetic evidence used to convict Knox and Sollecito in 2009.

Kercher was found slain in a pool of blood in the house she shared with Knox in Perugia. The appeals court in October said the guilty verdicts against the pair were not corroborated by any evidence, and that the court hadn't proven they were in the house when Kercher was killed.

Still, the appellate panel stopped short of saying what might have happened the night of the murder.

A third defendant, Ivory Coast-born drifter Rudy Guede, was convicted in a separate trial of sexually assaulting and stabbing Kercher. His 16-year sentence, reduced in appeal from an initial 30 years, was upheld by Italy's highest court in 2010.